In recent years, as camera-attached cell phones to which cameras are mounted became widespread, photographing various subjects with the cell phones has been done with increasing frequency. For example, pictures of subjects separated from the camera lens at a certain degree, such as friends or landscapes, may be taken (regular photographing), or pictures of subjects positioned closely at the camera lens, such as bus schedules or petals, may be taken (tight close-up photographing).
In the case of tight close-up photographing (macro photographing), the camera lens must be placed at a position slightly closer to the subject side than the position of the lens during the ordinary photographing. Consequently, this type of photographing lens is equipped with a driving mechanism to displace and drive the lens in the optical axis direction, and this driving mechanism is driven by changing the switch so that the lens can be moved in the optical axis direction.
The lens drive unit disclosed in Japanese Kokai Patent 2005-37865 comprises a moving body equipped with a lens, and a fixed body which moves this moving body in the optical axis direction of the lens and, at the time, holds the moving body; a drive magnet is installed in the moving body and a drive coil and two yokes are installed in the fixed body. And, when energization of the drive coil is stopped, the magnetic adsorption between the drive magnet and the yoke is utilized to hold the moving body at a position close to any of the above-mentioned two yokes. Hence, this lens drive unit has such advantages as a simple construction, few parts and suitability for miniaturization.
The lens drive unit disclosed in Japanese Patent Application Publication 2005-128392 moves a lens support body along the optical axis direction of the lens by electromagnetic force generated by supplying a current to coils. And in the absence of an electric current supplied to coils, two springs energizes (presses) the lens support body against the base. Under this condition, when the camera is not in use, the lens support body is unlikely to experience shaking or loosening.
On the other hand, the lens drive unit disclosed in Japanese Patent Application Publication 2005-165058 moves a lens holder along the optical axis direction of the lens caused by means of the electromagnetic force when a current is supplied to coils. It comprises a holder contact section to control the motion of lens holder and a holder spring to energize the lens holder. The holder contact section controls the range within which the lens holder can move excluding the neutral position where the holder spring is in the neutral state. In this way, the holder spring constantly applies its force to the lens holder, thereby improving shock resistance.
However, since the lens drive unit disclosed in Japanese Patent Application Publication 2005-128392 and Japanese Patent Application Publication 2005-165058 holds the lens unit (the lens support component or the lens holder mentioned above) by relying on the energizing force of the spring as described above, unstabilizing alignment accuracy becomes unstable; this is a problem.
That is, generally strains or burrs occur in springs made by press processing, and variations in spring constants result in unstable alignment accuracy. On the contrary, springs made by etching can reduce variations in spring constants to a certain degree; however, this type provides poor productivity, thus increasing manufacturing costs.
The present invention was made in view of the above problems, and its objective is to provide a lens drive unit which can stabilize stationary position accuracy of the lens unit.